The application relates to a method for the manufacture of a container, sealed in sterile manner by a foil or film and comprising a container body and at least one closure placed over the foil or film, as well as to a container manufactured by this method.
In the food and feed industry in many cases there is a need to seal, in a microbiologically sterile manner, a container in which the food or feed is packed. A microbially sterile seal can be achieved with the most varied methods, which range from the preserving jar, via various can closures to tray containers with pull-off foil lids. Particularly in those cases where it is simultaneously sought to provide a manually easily openable lid closure, it must be ensured by additional measures that, in the case of an unintentional opening of the can or container during storage, transportation, etc. the necessary microbiological sterility of the container content is ensured up to the time of intended opening by the consumer. It has been proposed for such cases that the container interior is initially sealed in microbiological sterile manner by a bonded or welded on foil and over said foil closure, particularly for greater stability and durability of the closure during storage, transportation, etc., is provided a stronger lid closure.
However, this type of container closure suffers from the disadvantage that it is necessary to fit in two separate steps two different closures, namely the foil closure for microbiological sterile sealing and the lid closure placed above the latter for increasing stability and durability, which gives rise to higher time and equipment costs and therefore higher overall costs.
Therefore the problem overcome by the present invention is to obviate the disadvantages of the prior art and make available a method with which, particularly in the last-discussed cases, a microbiologically sterile and storage and transportation-stable closure of a container can be inexpensively and easily manufactured.
In the case of the aforementioned method, the invention solves this problem in that prior to the closure of the container with the closure, on the side facing the container interior after closing, a foil is laminated and that the entire container closed with the closure undergoes a heat treatment at a sterilization and pasteurization temperature for the container content adequate to bond the foil to the wall of the container body in the vicinity of the closure. Thus, during a subsequent removal of the closure, because of a higher adhesion between foil and container body than between foil and closure, the foil remains adhering to the container body.
According to a preferred embodiment of the invention, the heat treatment takes place at a temperature of at least 50xc2x0 C.
According to a preferred embodiment of the invention, a coextruded material is used for the foil and is preferably a coextruded material based on polyethylene and polypropylene.
The invention also relates to a container manufactured according to the inventive method.
By means of the method according to the invention, it is possible to obviate the hitherto necessary method step of microbially sterile sealing of the container after filling by bonding or welding on a foil. The method according to the invention uses the temperatures necessary for the heat treatment, such as the sterilization or pasteurization of the container content, in order to bond a foil laminated on the closure to the container wall and consequently achieve the desired, two-part sealing of the container, which comprises the microbiologically sterile sealing by the foil and the lid closure giving the necessary stability for storage, transportation, etc.